What are mail servers
Mail servers are computer servers that handle email communication between email clients, such as Microsoft Outlook, Mozilla Thunderbird, or web-based email services like Gmail or Yahoo Mail. They play a crucial role in the email delivery process, ensuring that emails are sent, received, and stored securely.
Here's a simplified overview of how mail servers work:
- Mail Submission: When you send an email from your email client, it connects to a mail submission server (also known as a mail relay or mail forwarder). This server is responsible for accepting incoming emails and forwarding them to the next hop in the delivery process.
- Mail Relay: The mail submission server forwards the email to a mail relay server, which is responsible for routing the email to its final destination. Mail relays are often used to filter out spam, viruses, and other malicious content.
- Mail Server: The mail relay server forwards the email to a mail server, which is responsible for storing and managing the email. Mail servers can be configured to store emails on a local disk or in a database.
- Email Delivery: When a recipient checks their email, their email client connects to the mail server to retrieve their emails. The mail server retrieves the email from storage and sends it to the recipient's email client.
Mail servers can be categorized into two main types:
- Mail Transfer Agent (MTA): An MTA is responsible for transferring emails between mail servers. Examples of MTAs include Postfix, Sendmail, and Exim.
- Mail Delivery Agent (MDA): An MDA is responsible for delivering emails to the recipient's email client. Examples of MDAs include Procmail and Fetchmail.
Mail servers can also be configured to perform various functions, such as:
- Spam filtering: Filtering out spam emails using algorithms and blacklists.
- Virus scanning: Scanning emails for viruses and malware.
- Content filtering: Filtering out emails based on content, such as keywords or attachments.
- Authentication: Verifying the identity of senders and recipients using authentication protocols like SPF, DKIM, and DMARC.
In summary, mail servers play a vital role in the email delivery process, ensuring that emails are sent, received, and stored securely. They can be configured to perform various functions, such as spam filtering, virus scanning, and content filtering, to protect email users from malicious content.